Announcement

Collapse
No announcement yet.

Another vfd/motor question

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Another vfd/motor question

    I just got a monster compressor for the shop.

    A four cylinder "v" with a ten h.p. three phase motor.
    My five h.p. rotary inverter won't do it.
    I am thinking of putting the ten motor on the vfd and putting the five on the compressor with a pulley about half or third the size that was on the ten.

    Obviously I wont have the full volume of the compressor but should be plenty for my needs.

    I have #1 copper wire to the inverter through a 60 amp breaker. So I think the wiring is up to par.
    The inverter starter is rated at ten h.p.

    Am I missing the obvious?

    As soon as a kid shows up around here to show me how to post pictures I will show the rebuilt(ing) shop.

  • #2
    The smaller pulley should work.

    Yes, the ten as an RPC would run the 5 HP. Especially since there should be an unloader on the compressor, so it will start with no backpressure.

    Did not check the wire size, motor will pull about 50A max for 10 HP, you will not likely be that high as an RPC. If you also power the load through the same wires, you might get close to wire rating, which IIRC is about 110A for 60C rated wire.
    1601

    Keep eye on ball.
    Hashim Khan

    Comment


    • #3
      One thing to check if you are changing pulley sizes etc - the compressor will have a minimum speed rating to allow for adequate lubrication. Mine is 450 rpm, max 900. Yours may be different.

      HP requirements are also proportional to pressure developed; if your compressor was set to say 175psi, dropping it to 120 max will make a significant difference. With the larger volume, you may not need the 175 head. My large Quinicy runs at 90/120, 30cfm, and easily keeps up with my bead blaster etc.
      Last edited by lakeside53; 12-23-2017, 12:54 PM.

      Comment


      • #4
        Originally posted by lakeside53 View Post
        One thing to check if you are changing pulley sizes etc - the compressor will have a minimum speed rating to allow for adequate lubrication. Mine is 450 rpm, max 900. Yours may be different.

        HP requirements are also proportional to pressure developed; if your compressor was set to say 175psi, dropping it to 120 max will make a significant difference. With the larger volume, you may not need the 175 head. My large Quinicy runs at 90/120, 30cfm, and easily keeps up with my bead blaster etc.
        Do typical oil filled compressors circulate oil using the crank splashing oil everywhere within the crank case or do they have an active oil pump that forces oil through journals to bearing surfaces?

        Comment


        • #5
          Typical compressor use a splash lube system. REAL compressors use a pressure fed oil system. My three all have an oil pump.

          Comment

          Working...
          X